Electrode structure and battery device manufacturing method

ABSTRACT

An electrode is provided with a metal terminal extending from a battery module main body, a bolt which has an expanded section configuring a retaining section at a rear end portion and penetrates the metal terminal upward, and an insulating body which insulates the metal terminal and the battery module case one from the other. The insulating body is provided with a drop preventing section which abuts at least a lower surface of the expanded section of the bolt and prevents the bolt from dropping from the metal terminal.

This is a divisional application of application Ser. No. 12/522,005filed Jul. 2, 2009, which is a national phase application ofInternational Application No. PCT/JP2008/050657, filed Jan. 11, 2008,and claims the priority of Japanese Application Nos. 2007-004529, filedJan. 12, 2007, and 2007-211258, filed Aug. 14, 2007, the contents of allof which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an electrode structure and a method ofmanufacturing a battery device and, more specifically, to an electrodestructure for connecting a battery module to a bus bar and to a methodof manufacturing a battery device to which the bus bar is connected.

BACKGROUND ART

A battery device mounted on a hybrid vehicle or an electric vehicle hasa plurality of battery modules connected in series or in parallel. Theplurality of battery modules are connected to each other by a bus bar.The battery module is provided with an electrode to be connected to thebus bar.

For the connection to the bus bar, a bolt is attached to a metalterminal of the electrode. The bolt attached to the metal terminalpenetrates through the bus bar, and screw-fixed in a nut, so that thebus bar is firmly fixed.

Considering the process step of attaching the bus bar to the electrode,it is preferred to have the bolt temporarily fixed in advance on themetal terminal. As a method of such temporary fixing of the bolt, it maybe possible to insert the bolt with pressure to a through hole providedin the metal terminal.

Japanese Patent Laying-Open No. 2002-8627 (Patent Document 1) disclosesbattery modules connected by such a bus bar. According to PatentDocument 1, a plurality of cylindrical battery modules are connected bya plate-shaped bus bar.

Japanese Patent Laying-Open No. 7-226197 (Patent Document 2) discloses abattery for a portable electric device, having an easily bendable partwith reduced width or thickness between an electrode plate and aconnecting part of a relay lead.

DISCLOSURE OF THE INVENTION

When the bolt is inserted with pressure to the metal terminal fortemporarily fixing the bolt on the metal terminal, there is a problemthat a fastening surface of the metal terminal may be deformed at thestep of insertion with pressure. Further, for temporary fixing of thebolt, the step of inserting bolt to the metal terminal with pressurebecomes necessary, leading to increased number of process steps.

The present invention was made to solve the above-described problems,and its object is to provide an electrode structure and a method ofmanufacturing a battery device that allows temporary fixing of the bolton the metal terminal in an easy manner.

The present invention provides an electrode structure for connecting abattery module to a bus bar, including: a metal terminal extending froma body of the battery module; a bolt having an expanded section forminga retaining section at a rear end, and penetrating the metal terminalupward; and an insulator insulating the metal terminal and a case of thebattery module from each other; wherein the insulator has a droppreventing section abutting on at least the expanded section of the boltfrom below to prevent dropping of the bolt from the metal terminal.

In the electrode structure described above, preferably, the metalterminal has a fixing piece fixed to the case through the insulator, aconnecting piece continuous from the fixing piece in a bending directionand having at least the portion continuous from the fixing pieceextending in a direction away from the case, and a terminal piececontinuous from the connecting piece in a bending direction and having athrough hole through which the bolt penetrates. At this time, distancebetween the fixing piece and the terminal piece in a direction away fromthe case may be at least 50% of the width of the connecting piece and atleast 5 times the thickness of the connecting piece.

In the electrode structure described above, preferably, the expandedsection has a lower surface and a side surface; the drop preventingsection has two abutting surfaces positioned in orthogonallyintersecting directions with each other, with one abutting surfaceabutting on the lower surface of the expanded section and the otherabutting surface abutting on the side surface of the expanded section.

In the electrode structure described above, preferably, the droppreventing section has a wall portion surrounding an outer periphery ofthe expanded section.

In the electrode structure described above, preferably, a plurality ofbent portions are provided between the fixing piece and the terminalpiece, and at least one of the plurality of bent portions is formed tobe a stiffness reduced portion smaller in at least one of thickness andwidth than other portions of the metal terminal.

In the electrode described above, the stiffness reduced portion may beformed by depressing an inside corner of the bent portion in a dent todraw a curve.

The present invention also provides a method of manufacturing a batterydevice, including the steps of arranging a plurality of battery modulesincluding an electrode provided with a metal terminal extending from abody of the battery module, a bolt having an expanded section forming aretaining section at a rear end, and penetrating the metal terminalupward, and an insulator having a drop preventing section abutting on atleast the expanded section of the bolt from below to prevent dropping ofthe bolt from the metal terminal and insulating the metal terminal and acase of the battery module from each other; attaching a bus barelectrically connecting the electrodes by inserting the bolt to athrough hole provided in the bus bar; and fixing the bus bar byfastening a nut to the bolt.

In the method of manufacturing a battery device described above,preferably, the metal terminal has a fixing piece fixed to the casethrough the insulator, a connecting piece continuous from the fixingpiece and extending in a direction away from the case, and a terminalpiece continuous from the connecting piece, extending approximatelyparallel to said fixing piece, and having a through hole through whichthe bolt penetrates.

Two or more of the above-described structures may be combined.

According to the electrode structure and the method of manufacturing thebattery device of the present invention, temporary fixing is attained byan insulator and, therefore, the bolt can easily be fixed temporarily onthe metal terminal. Further, using the temporarily fixed bolt, the busbar can be attached easily to the electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a structure of a battery device inaccordance with Embodiment 1 of the present invention.

FIG. 2 is a side view of a battery module in accordance with Embodiment1 of the present invention.

FIG. 3 is a vertical sectional view of the battery module in accordancewith Embodiment 1 of the present invention.

FIG. 4 is a vertical sectional view of an electrode in accordance withEmbodiment 1 of the present invention.

FIG. 5 is an exploded perspective view of the electrode in accordancewith Embodiment 1 of the present invention.

FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 1,showing a structure of the battery device in accordance with Embodiment1 of the present invention.

FIG. 7 is a perspective view showing a structure of a joint portion inaccordance with Embodiment 1 of the present invention.

FIG. 8 is an enlarged view of a portion A of FIG. 6, showing thestructure of an electrode in accordance with Embodiment 1 of the presentinvention.

FIG. 9 is a cross-sectional view taken along the line IX-IX of FIG. 1,showing the structure of the electrode in accordance with Embodiment 1of the present invention.

FIG. 10 is an enlarged view of the portion b of FIG. 9, showing thestructure of the electrode in accordance with Embodiment 1 of thepresent invention.

FIG. 11 is a vertical sectional view showing a structure of an electrodein accordance with Embodiment 2 of the present invention.

FIG. 12 is a vertical sectional view showing a structure of an electrodein accordance with Embodiment 3 of the present invention.

FIG. 13 is a plan view showing the structure of the electrode inaccordance with Embodiment 3 of the present invention.

FIG. 14 shows how easily the metal terminal in accordance withEmbodiment 3 of the present invention deforms.

FIG. 15 is a vertical sectional view showing a structure of a referenceexample provided with a portion of reduced stiffness.

BEST MODES FOR CARRYING OUT THE INVENTION

In the following, the electrode structure and the method ofmanufacturing a battery device in accordance with various embodiments ofthe present invention will be described with reference to the figures.In these embodiments, the same or corresponding portions are denoted bythe same reference characters, and accumulative description will not berepeated.

Embodiment 1

FIG. 1 is a plan view showing a structure of a battery device inaccordance with the present embodiment. As shown in FIG. 1, a batterydevice 1 has a plurality of battery modules 11. In battery device 1shown in FIG. 1, battery modules 11 are arranged in two rows with theirmain surfaces positioned parallel to each other. Though an example inwhich battery modules 11 are arranged in two rows is shown here, themodules may be arranged in one row or in three or more rows.

Each battery module 11 has electrodes 21 serving as positive andnegative electrodes, respectively. Electrodes 21 of battery modules 11arranged side by side are connected to each other by a bus bar 81. Busbar 81 is formed of plate-shaped metal.

At an end portion of the thus arranged plurality of battery modules 11,a binding plate 91 is provided. Binding plates 91 apply a force incompressing direction, to the thus arranged plurality of battery modules11 from opposite end portions. Consequently, battery modules 11 are keptin the arranged state and appropriate pressure is applied to eachbattery module.

At the end portion opposite to the thus arranged plurality of batterymodules 11, similar binding plate is also provided, though not shown.These two binding plates 91 are coupled by a coupling member, not shown.

FIG. 2 is a side view of the battery module in accordance with thepresent embodiment, FIG. 3 is a vertical sectional view of the same,FIG. 4 is a vertical sectional view of the electrode, and FIG. 5 is anexploded perspective view of the electrode. Battery module 11 has abattery cell 12 provided inside. Battery cell 12 is housed in a batterycase 13. Battery cell 12 may be any rechargeable secondary battery andnot specifically limited. By way of example, it may be a nickel hydridebattery or a lithium ion battery. Though FIG. 2 shows an example inwhich one battery cell 12 is housed in one battery case 13, a pluralityof battery cells may be housed. In the present specification, thebattery module encompasses one having a plurality of battery cellsprovided in the battery case and one having one battery cell provided inthe battery case. Further, in the present specification, the batterycell means a minimum unit that functions as a rechargeable secondarybattery.

Battery case 13 includes a battery case body 13 a and a lid 13 b. Inorder to provide adequate strength, battery case 13 is formed, forexample, of a galvanized sheet steel. Battery case body 13 a has a boxshape with a space inside and open only at the upper plane. Lid 13 b hasa plate shape. To lid 13 b, a pair of electrodes 21 serving as positiveand negative electrodes are attached. These electrodes 21 areelectrically connected to battery cell 12 housed in battery case 13.

As shown in FIGS. 4 and 5, electrode 21 includes a metal terminal 41, abolt 31 having its tip end protruded upward from metal terminal 41, anda rivet 51 fixing metal terminal 41 to lid 13 b.

In the present embodiment, metal terminal 41 has an approximatelyZ-shape when viewed from the side. Specifically, metal terminal 41includes a fixing piece 41 a fixed to lid 13 b, a connecting piece 41 bbent at a right angle from fixing piece 41 a and extending in adirection away from lid 13 b, and a terminal piece 41 c continuous toconnecting piece 41 b and parallel to the fixing piece 41 a. Fixingpiece 41 a and terminal piece 41 c have through holes. Rivet 51 passesthrough the through hole of fixing piece 41 a, and bolt 31 passesthrough the through hole of terminal piece 41 c. Though connecting piece41 b is bent at a right angle with respect to fixing piece 41 a andterminal piece 41 c, the angle is not necessarily be a right angle.

Further, connecting piece 41 b may not necessarily have a plate shape,and may have a bent shape. For instance, connecting piece 41 b may havetwo bent portions and have an approximately Z shape when viewed from theside. Specifically, connecting piece 41 b may be formed to include afirst portion, continuous to the fixing piece 41 a in the bendingdirection and extending in a direction away from box 13, a secondportion continuous to the first portion in the bending direction, and athird portion continuous to the second portion in the bending directionand further, at an end portion, continuous to the terminal piece 41 c inthe bending direction.

As terminal piece 41 c and fixing piece 41 a are connected by connectingpiece 41 b, terminal piece 41 c and fixing piece 41 a are off-set. Metalterminal 41 is formed by bending a metal plate.

In the present embodiment, the distance D in the direction alongconnecting piece 41 b between fixing piece 41 a and terminal piece 41 cshown in FIGS. 4 and 5 is set to be at least 50% of the width W ofconnecting piece 41 b and at least 5 times the thickness T of connectingpiece 41 b. More specifically, in the present embodiment, the distance Din the direction along connecting piece 41 b between fixing piece 41 aand terminal piece 41 c is set to be 50% of the width W of connectingpiece 41 b and 6 times the thickness T of connecting piece 41 b.

In the present embodiment, the width W of connecting piece 41 b is madeequal to the width of fixing piece 41 a and terminal piece 41 c. Thewidth W of connecting piece 41 b, however, may be made smaller than thewidth of fixing piece 41 a and terminal piece 41 c. Further, connectingpiece 41 b may be formed to have a narrowed portion.

In the present embodiment, the thickness T of connecting piece 41 b ismade equal to the thickness of fixing piece 41 a and terminal piece 41c. The thickness T of connecting piece 41 b, however, may be madesmaller than the thickness of fixing piece 41 a and terminal piece 41 c.Further, connecting piece 41 b may be formed to have a thinner portion.

At a lower end of bolt 31, an expanded section 35 is formed. Expandedsection 35 is made larger than the shaft portion of bolt 31 and servesas a retention, and formed to have a rectangular shape when viewedtwo-dimensionally. Though expanded section 35 is formed to have arectangular shape when viewed two-dimensionally here, it may have otherpolygonal shape such as a hexagon, or other shape having a recess orprotrusion to be engaged with an abutting portion. Expanded section 35has a bottom surface and a side surface. At the bottom surface ofexpanded section 35, a horizontally extending trench 36 is formed. Thetrench on the bottom surface of expanded section 35 may be omitted, andthe bottom may be formed flat.

Between fixing piece 41 a of metal terminal 41 and lid 13 b, aninsulator 43 is provided. Insulator 43 insulates metal terminal 41 fromlid 13 b, and functions as a gasket sealing the through hole of lid 13b. Insulator 43 includes a base plate portion 44 extending along anupper surface of lid 13 b, and a drop preventing section 45 protrudingupward from base plate portion 44 for temporarily fixing bolt 31.Insulator 43 may be formed of any insulating material and, by way ofexample, it is formed of synthetic resin. Here, polyphelylene sulfide(PPS) resin or nylon is used.

On the lower surface of base plate portion 44 of insulator 43, aring-shaped protrusion 44 a is provided, which is inserted to thethrough hole of lid 13 b. On the upper surface of base plate portion 44,fixing piece 41 a of metal terminal 41 is arranged. At an outerperiphery of base plate portion 44, a peripheral wall 44 b is formed,surrounding outer periphery of fixing piece 41 a of metal terminal 41.As the fixing piece 41 a of metal terminal 41 is surrounded byperipheral wall 44 b, more reliable insulation between metal terminal 41and lid 13 b is realized.

Insulator 43 has drop preventing section 45 provided below terminalpiece 41 c. Drop preventing section 45 is integrally molded with baseplate portion 44. Drop preventing section 45 protrudes toward a portionof a lower surface of expanded section 35 of bolt 31. Drop preventingsection 45 has a horizontal abutting surface 45 a that abuts on thelower surface of expanded section 35 and a vertical abutting surface 45b that abuts on a side surface of expanded section 35.

Since the lower surface of expanded section 35 abuts on the horizontalabutting surface 45 a, dropping of expanded section 35 from terminalpiece 41 c of metal terminal 41 can be prevented. Further, since theside surface of expanded section 35 abuts on vertical abutting surface45 b, large inclination of bolt 31 can be prevented. Vertical abuttingsurface 45 b may be omitted. Further, it is not absolutely necessarythat the horizontal abutting surface 45 a is horizontal. It may havevarious shapes in accordance with the shape of expanded section 35 ofbolt 31.

At a lower end of rivet 51, a seat 52 of rectangular metal plate isprovided. To seat 52, a terminal 71 extending downward is connected asshown in FIG. 3, which terminal 71 is electrically connected to batterycell 12.

Between the upper surface of seat 52 and lid 13 b, an insulating member58 is arranged. Outer peripheral portion of insulating member 58 issuspended downward, surrounding outer periphery of seat 52. For theinsulating member 58, a material hard to degrade in an environment inbattery case 13 should be used. Here, PPS resin is used.

A ring-shaped gasket 59 is provided to be in tight-contact with an outercircumference of a shaft of rivet 51. Gasket 59 is positioned inside thethrough hole of insulating member 58, and an upper surface of gasket 59is in contact with the circumference of through hole in lid 13 b. Thisrealizes more reliable tight-sealing of battery case 13. For the gasket,a resin or rubber material may be used.

When electrode 21 is fixed on lid 13 b, bolt 31 is inserted beforehandto terminal piece 41 c of metal terminal 41, and rivet 51 is inserted insuch an order as shown in FIG. 5. In this state, the tip end of rivet iscrimped and enlarged, so that electrode 21 is fixed on lid 13 b.

At this time, bolt 31 is simply inserted to metal terminal 41 and notyet fixed. The lower surface of expanded section 35 of bolt 31, however,abuts on horizontal abutting surface 45 a of drop preventing section 45.Therefore, dropping of bolt 31 from metal terminal 41 can be prevented.

Therefore, it is possible to maintain a state in which bolt 31 is heldby metal terminal 41 from the completion of battery module 11 to thenext process step, without the necessity of adding any special step suchas insertion of bolt 31 with pressure to metal terminal 41.

When battery device 1 is manufactured, first, a plurality of batterymodules 11 are arranged. Thereafter, a bus bar 81 for electricallyconnecting electrodes of battery modules 11 is attached by insertingbolt 31 to the through hole provided in bus bar 81, and by fastening nut39 to bolt 31, bus bar 81 is fixed. During these process steps, bolt 31is held by drop preventing section 45 and, therefore, it will not dropfrom metal terminal 41.

Since drop preventing section 45 is formed integrally with base plateportion 44 for insulation and tight-sealing, the number of process stepsis not increased for attaching drop preventing section 45. Further, thenumber of components is not increased, either. In this manner, bolt 31can easily be held by metal terminal 41.

Further, the step of inserting bolt 31 with presser to metal terminal 41can be eliminated and, therefore, deformation of metal terminal 41 inthe pressure-insertion step can be prevented. This leads to improvedpositional accuracy of bolt 31, and hence, to smoother attachment of busbar 81.

In the present embodiment, metal terminal 41 is formed to include fixingpiece 41 a fixed to lid 13 b, connecting piece 41 b bent at a rightangle from fixing piece 41 a and extending in a direction away from lid13 b, and terminal piece 41 c continuous to connecting piece 41 b andparallel to the fixing piece 41 a. Bolt 31 is inserted to terminal piece41 c, and nut 39 is fastened to bolt 31 to fix bus bar 81. In thepresent embodiment, fixing piece 41 a and terminal piece 41 c areoff-set and connected by connecting piece 41 b and, therefore, in thisstep of fastening nut 39, moment exerted on terminal 41 c is absorbed bydeformation of connecting piece 41 b and not much transmitted to fixingpiece 41 a. Fixing piece 41 a is fixed to lid 13 b by rivet 51, andundesirable influence to this fixing structure can be minimized.

Effects attained by adopting metal terminal 41 of such a shape will bedescribed in greater detail. In a battery module, the fixing portion ofelectrode 21 to the body of battery module is a very important portionin order to ensure the following functions. First, rivet 51 used forfixing functions as an electrical conduction member between metalterminal 41 and battery cell 12. Second, insulator 43 crimped and fixedsimultaneously by rivet 51 ensures insulation of battery case 13 fromelectrode 21 and rivet 51. Third, insulator 43 fixed by rivet 51 alsofunctions to ensure tight-sealing at the fixing portion. In order toreliably attain these functions, it is preferred that as small stress aspossible is transmitted through metal terminal 41 to rivet 51 andinsulator 43 positioned at the fixing portion.

Such being the case, if the electrode were formed of a flat metal plate,the stress of fastening the nut would be directly transmitted throughthe electrode to the fixing portion. In that case, if a high stress wereapplied to the rivet, for example, the rivet would possibly be loosened,or the insulator would possibly be deformed. This possibly leads to afailure of electrical conduction at the rivet, or insufficientinsulation or insufficient tight-sealing by the insulator.

In contrast, according to the present embodiment, since the fixing piece41 a and terminal piece 41 c are connected by connecting piece 41 b andthereby fixing piece 41 a and terminal piece 41 c are off-set, even whena high stress is applied to terminal piece 41 c, connecting piece 41 bdeforms and alleviates the stress applied to the fixing portion. As aresult, possibility of the above-described problems can be reduced.

Here, in the present embodiment, the distance D in the direction alongthe connecting piece 41 b between fixing piece 41 a and terminal piece41 c shown in FIGS. 4 and 5 is set to be at least 50% of the width W ofconnecting piece 41 b and at least 5 times the thickness T of connectingpiece 41 b. Therefore, stiffness of connecting piece 41 b issufficiently small. Accordingly, if a high stress is applied to terminalpiece 41 c, connecting piece 41 b deforms sufficiently to reliablyreduce the stress to be applied to the fixing portion. If the distance Din the direction along the connecting piece 41 b between fixing piece 41a and terminal piece 41 c shown in FIGS. 4 and 5 is smaller than 50% ofthe width W of connecting piece 41 b or smaller than 5 times thethickness T of connecting piece 41 b, connecting piece 41 b has highstiffness and does not deform sufficiently. Thus, the effect ofalleviating the stress applied to the fixing portion becomes weak.

Further, since terminal piece 41 c and fixing piece 41 a are connectedby connecting piece 41 b, a space is formed below terminal piece 41 c,which space can be utilized as a space for accommodating the expandedsection 35 of bolt 31 and for drop preventing section 45.

FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 1,showing a structure of the battery device, and FIG. 7 is a perspectiveview showing the structure of the contact portion. As described above,battery device 1 includes a plurality of battery modules 11 arranged inparallel. A holding member 61 is arranged in a space between each of thebattery modules 11. Holding member 61 includes a plurality of ribs 63extending in the horizontal direction. A space between ribs 63 forms anair passage 62, and cooling air is supplied to air passage 62. Coolingair cools surfaces of battery modules 11, and reduces heat of batterymodules 11. Namely, holding member 61 has a function of cooling batterymodules 11.

One surface of holding member 61 and a tip end of each rib 63 are incontact with the surface of battery module 11. Holding member 61 pressesthe surface of battery module 11 and maintains a constant space to anadjacent battery module, and holds the plurality of modules 11 not to beout of alignment. Holding member 61 is formed of molded resin. Since theholding member 61 is formed of an insulator such as resin, insulationbetween neighboring battery modules can be ensured.

At an upper end of holding member 61, an abutting portion 64 isprovided, which abuts on expanded section 35 of bolt 31. Abuttingportion 64 abuts on expanded section 35 of bolt 31, to prevent rotationof bolt 31 when nut 39 is fastened.

FIG. 8 is an enlarged view of portion A of FIG. 6. As shown in FIGS. 7and 8, abutting portion 64 has a vertical wall portion 64 a abutting ona side surface of expanded section 35 of bolt 31, and a horizontalprojection 64 b to be inserted to a trench 36 on a lower surface ofexpanded section 35.

Referring to FIG. 8, there is a space between expanded section 35 andvertical wall portion 64 a and horizontal projection 64 b. When torqueis applied to the nut for fastening nut 39, expanded section 35 rotatesaccordingly. At this time, expanded section 35 comes to abut on one orboth of the vertical wall portion 64 a and horizontal projection 64 b ofabutting portion 64 and, as a result, co-rotation can be prevented.Expanded section 35 of bolt 31 has a rectangular shape when viewedtwo-dimensionally and, hence, it has a pair of sides extending inparallel. These sides abut opposite vertical wall portions 64 a ofadjacent holding member 61. As the two sides of expanded section 35abut, larger torque can be accommodated.

In order to more effectively prevent co-rotation of bolt 31, frictionstabilizing agent may be applied to increase coefficient of frictionbetween metal terminal 41 and expanded section 35 of bolt 31.

FIG. 9 is a cross-sectional view taken along the line IX-IX of FIG. 1,showing the structure of the battery module, and FIG. 10 is an enlargedview of portion b of FIG. 9. As described above, trench 36 is providedat the bottom surface of enlarged section 35 of bolt 31, and in trench36, horizontal projection 64 b of abutting portion 64 is positioned.When torque is applied to nut 39 and expanded section 35 co-rotates,inner side surface of trench 36 comes to abut on the side surface ofhorizontal projection 64 b.

In the present embodiment, vertical wall portion 64 a is adapted to abuton the side surface of expanded section 35 and horizontal projection 64b is adapted to abut on the inner side surface of trench 36 at thebottom surface of expanded section 35 and, therefore, even when a hightorque is applied, co-rotation of bolt 31 can surely be prevented. It isnoted, however, that the structure of abutting portion 64 may bedetermined as needed, and only the vertical wall portion 64 a may beadapted to abut, in order to prevent co-rotation of bolt 31.

Further, since the torque applied to nut 39 is received by abuttingportion 64 provided at holding member 61, the force applied to metalterminal 41 can be reduced. This can alleviate undesirable deformationand the like of metal terminal 41. As shown in FIG. 8, on abuttingportion 64 of holding member 61, bolt 31 of adjacent electrode 21 abuts.However, since the holding member 61 is formed of an insulating materialas described above, insulation between electrodes 21 can be ensured.

Here, expanded section 35 of bolt 31 is formed to have a rectangularshape when viewed two-dimensionally, and its side surface abuts onvertical wall portion 64 a. It is also possible to form a recess or aprotrusion around the expanded section 35 of bolt 31, and to provide anabutting portion having a shape matching the recess or the protrusion.

Embodiment 2

Next, Embodiment 2 will be described with reference to FIG. 11. FIG. 11is a vertical sectional view showing a structure of an electrode, and itcorresponds to FIG. 10 of Embodiment 1.

In the present embodiment, the structure of insulator 43 is changed suchthat insulator 43 serves to prevent dropping and co-rotation of bolt 31.Specifically, insulator 43 is formed to surround expanded section 35 ofbolt 31, and expanded to fill the space between the lower side of bolt31 and lid 13 b, to form drop preventing section 45. Further, at a lowersurface of insulator 43 and lower side of drop preventing section 45, anengaging projection 46 is formed, protruded downward.

Expanded section 35 of bolt 31 abuts on drop preventing section 45 and,therefore, dropping from metal terminal 41 is prevented. Further, as theexpanded section 35 of bolt 31 is surrounded by wall portion 47 providedin drop preventing section 45, rotation of expanded section 35 isprevented by drop preventing section 45 when torque is applied to nut39, and hence, co-rotation can be prevented.

At this time, as the engaging projection 46 is provided at the bottomsurface of insulator 43 and engaging projection 46 is inserted torecessed portion 13 c of lid 13 b, positional deviation of insulator 43can be prevented, and co-rotation of bolt 31 can more reliably beprevented.

Further, metal terminal 41 in accordance with the present embodiment hasthe same shape as that of Embodiment 1. Therefore, as in Embodiment 1,even when large stress is applied to the terminal piece 41 c, connectingpiece 41 b deforms and, therefore, the stress applied to the fixingportion between metal terminal 41 and case 13 can be alleviated.

Embodiment 3

Next, Embodiment 3 will be described with reference to FIGS. 12 and 13.FIG. 12 is a vertical sectional view showing a structure of anelectrode, and it corresponds to FIG. 10 of Embodiment 1. FIG. 13 is aplan view of the battery module in accordance with the presentembodiment. FIG. 13 shows a state before bus bar 81 is attached.

In the present embodiment, as in Embodiment 2, insulator 43 serves toprevent dropping and co-rotation of bolt 31. Further, in the presentembodiment, stiffness reduced portion is formed at the bent portion ofmetal terminal 41.

In the present embodiment, expanded section 35 of bolt 31 is formed tohave a hexagonal shape, and a flange 35 a is provided on the screw-sideend of expanded section 35. Flange 35 a protrudes outward from the bodyof expanded section 35.

Drop preventing section 45 of insulator 43 is provided with a wallportion 47 that surrounds expanded section 35 of bolt 31. Wall portion47 forms a hexagonal recess, to which the hexagonal body of expandedsection 35 is inserted. Since the expanded section 35 is inserted to therecess formed by wall portion 47, co-rotation of bolt 31 can beprevented when torque is applied to nut 39.

Further, an upper end of wall portion 47 abuts on flange 35 a frombelow, and therefore, bolt 31 is prevented from dropping down.

At a lower surface of insulator 43 and below drop preventing section 45and wall portion 47, an engaging projection 46 is provided, projectingdownward. Engaging projection 46 is inserted to a recess 13 c of lid 13b. This prevents significant positional deviation of insulator 43 and,hence, co-rotation of bolt 31 can more reliably be prevented.

Metal terminal 41 has, as in Embodiment 1 and Embodiment 2, fixing piece41 a, connecting piece 41 b continuous to fixing piece 41 a in a bendingdirection, and terminal piece 41 c continuous to connecting piece 41 bin the bending direction.

Further, as in Embodiment 1, connecting piece 41 b may not necessarilyhave a plate shape, and may have a bent shape. For instance, connectingpiece 41 b may have two bent portions and have an approximately Z shapewhen viewed from the side.

At a bent portion 41 t positioned at a boundary between fixing piece 41a and connecting piece 41 b and a bent portion 41 u positioned at aboundary between connecting piece 41 b and terminal piece 41 c of metalterminal 41, inside corner (inner angle side of bent portion) isdepressed in a dent to draw a curve, to form stiffness reduced portions.Inner surface of dents at bent portions 41 t and 41 u forming thestiffness reduced portions do not necessarily have a curved surface.

Consequently, in the step of fastening bus bar 81 by applying torque tonut 39, bent portions 41 t and 41 u forming the stiffness reducedportions deform, and therefore, transmission of the fastening forceapplied to nut 39 to fixing piece 41 a can be reduced. Thus, possibilityof loosening of rivet 51 and deformation of insulator 43 or gasket 59can be reduced.

Particularly, if any force is applied in a direction of moving terminalpiece 41 c upward/downward, it is transmitted as the force moving fixingpiece 41 a upward/downward. Therefore, such force is problematic as itleads to loosening of rivet 51. In the structure of the presentembodiment, bent portions 41 t and 41 u are depressed to have dents and,therefore, stiffness can be lowered particularly with respect to theforce in the direction of moving terminal piece 41 c upward/downward.Consequently, the problematic loosening of rivet 51 can effectively beprevented. As a result, degradation of sealing effect attained byinsulator 43 or gasket 59 can effectively be prevented.

Further, in the present embodiment, dents are formed to draw a curve atthe inside corners of bent portions 41 t and 41 u and, as a result,radius of curvature at the inside corner becomes larger. This alleviatesstress concentration at the inside corners of bent portions 41 t and 41u. As a result, decrease in strength of bent portions 41 t and 41 u canbe minimized.

In addition, in the present embodiment, the stiffness reduced portionsare provided only in the bent portions 41 t and 41 u. If the stiffnessis simply to be reduced, plate thickness of metal terminal 41 may bereduced for the entire length. If the plate thickness is reduced for theentire length of metal terminal 41, the ratio of cross sectionalarea/surface area of metal terminal 41 decreases, resulting in a problemof heat build-up caused by self-heating. By reducing plate thicknesslocally as in the present embodiment, decrease in the ratio of crosssectional area/surface area can be minimized.

Though the stiffness reduced portions are formed by providing dents onthe inside corners of bent portions 41 t and 41 u in the presentembodiment, it is also possible to form the stiffness reduced portion bygrinding down the outside corner (outer angle side of bent portion).

Only one of the bent portions 41 t and 41 u may be processed to be thestiffness reduced portion.

As described above, a bent portion may be provided in connecting piece41 b so that connecting piece 41 b has a bent shape. In that case, thebent portion inside connecting piece 41 b may also be formed as astiffness reduced portion. Further, bent portions 41 t and 41 u may notbe formed as the stiffness reduced portions and only one or more of thebent portions inside the connecting piece 41 b may be formed as thestiffness reduced portions.

Further, it is also possible to form the stiffness reduced portion bymaking narrower the width of metal terminal 41 only at bent portions 41t and 41 u. The stiffness reduced portion may be formed by thecombination of these methods.

The stiffness reduced portion at the bent portion of metal terminal 41as described with reference to Embodiment 3 may also be formed in thestructures of Embodiment 1 and Embodiment 2.

FIG. 14 shows how easily the metal terminals deform to load, comparingthe metal terminal provided with the stiffness reduced portion inaccordance with the present invention and a metal terminal not providedwith the stiffness reduced portion.

As shown in FIG. 14, when the stiffness reduced portion is provided,deformation is 1.5 times higher to the same load, than when thestiffness reduce portion is not provided. Specifically, transmission ofexternal force can be reduced to ⅔. As a result, even if a forcesufficient to cause compressed gasket 59 to expand 0.03 mm when thestiffness reduced portion is not provided, the expansion can be reducedto 0.02 mm when the stiffness reduced portion is provided. This securessqueeze of the sealing rubber and, typically, its life can be madelonger by about 5 to about 10 years.

FIG. 14 shows results of calculation when a metal plate having the platethickness of 1.0 mm was used and the minimum thickness at the stiffnessreduced portion was set to 0.7 mm.

FIG. 15 shows a reference example of a metal terminal 141 provided withthe stiffness reduced portion. Metal terminal 141 shown in FIG. 15 isbent only once. Specifically, it has an L-shape, with only one bentportion 141 t. An inside corner of bent portion 141 t is depressed toform a dent, so that the stiffness reduced portion thinner than otherportions is formed.

If there is one or more bent portions, it is possible to form thestiffness reduced portion at the bent portion. Therefore, the effect ofalleviating the force applied to terminal piece 141 c of metal terminal141 at the stiffness reduced portion and reducing transmission to fixedpiece 141 a can be attained.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the scopeof the present invention being interpreted by the terms of the appendedclaims.

INDUSTRIAL APPLICABILITY

The electrode structure and the method of manufacturing battery devicein accordance with the present invention allow temporary fixing with aninsulator. Therefore, temporary fixing of a bolt to a metal terminal canbe done easily. Further, using the temporarily fixed bolt, a bus bar caneasily be attached to the electrode.

The invention claimed is:
 1. A battery module with a case having abattery cell housed therein, comprising: a metal terminal having afixing piece provided with a through hole, and extending from said case;an insulator insulating said metal terminal and said case from eachother; and a rivet; said insulator having a ring-shaped protrusioninserted in a through hole provided through said case, said rivet fixingsaid fixing piece to said case through said through hole of said fixingpiece and said ring-shaped protrusion of said insulator.
 2. The batterymodule according to claim 1, wherein said insulator has a peripheralwall surrounding an outer periphery of said fixing piece of said metalterminal.
 3. The battery module according to claim 1, further comprisinga gasket in tight-contact with a tip of said ring-shaped protrusion andsaid rivet.
 4. The battery module according to claim 1, furthercomprising a bolt having an expanded section forming a retaining sectionat a rear end, and penetrating said metal terminal upward, wherein saidinsulator has a base plate portion extending along said case, and ahorizontal abutting surface formed integrally with said base plateportion and provided at a location protruding from said base plateportion upward, said expanded section having a lower surface abutting onsaid horizontal abutting surface.
 5. The battery module according toclaim 1, further comprising a bolt having an expanded section forming aretaining section at a rear end, and penetrating said metal terminalupward, wherein said insulator has a vertical abutting surface abuttingon a side surface of said expanded section.